Gene expression analysis has revealed that ethylene directly regulates
the transcription of both a softening-related PpPG gene
and an expansin (PpExp3), thus suggesting that the rapid loss
of firmness in ripening fruit is caused by cell wall metabolism,
and is controlled by ethylene at the transcriptional level
(Hayama et al., 2006). Moreover, PpPG2 and PpPME2 are
reported to be involved in ethylene-regulated solubilization
of polyuronides in peach fruit (Murayama et al., 2009). In
this study, we found that ethylene production and signalling
was affected by melatonin, and M50-fruit was softer than
CK-fruit (Fig. 3A). Our findings suggest that melatonin may
influence ethylene to regulate fruit textural changes.